-LRB- CNN -RRB- -- Five people have been killed after one of the Philippines ' most active volcanoes spewed a giant cloud of ash and rocks early Tuesday .

They were climbing on Mount Mayon , some 212 miles -LRB- 340 km -RRB- southeast of Manila , when the blast occurred at around 8 a.m. local time , according to the National Disaster Risk Reduction and Management Council -LRB- NDRRMC -RRB- .

Of the five fatalities , four were German tourists , while the other was identified as Jerome Berin , their Filipino guide , the NDRRMC said . Joey Salceda , governor of Albay Province , told CNN affiliate ABS-CBN they were killed after being hit by falling rocks . He said they were part of a larger group scaling the volcano . Seven others , including an Australian , were hurt .

The NDRRMC said a total of 27 hikers were on the volcano at the time and requested assistance .

iReport : Volcano sends ash soaring into sky

According to the Philippine Institute of Volcanology and Seismology , the blast sent a thick column of ash 500 meters -LRB- 1,600 feet -RRB- into the air -- the result of what it called a `` small phreatic event '' that lasted about 73 seconds .

While no intensification of volcanic activity was observed , it warned that these sudden ash and steam explosions could occur at any time . Therefore officials advised people against going inside a six-kilometer danger zone around the volcano .

Mount Mayon is the most volatile of more than 50 volcanoes -- 22 of which are considered active -- that are scattered across the Philippine archipelago .

An almost perfect cone shape , Mayon last erupted in 2010 and forced thousands of people to flee from their homes . Mayon 's slopes , like many volcanoes in the country , are home to thousands of farming communities who make use of the fertile soils provided by the volcanic activity despite the occasional risk of eruption .

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Five climbers killed during ash explosion on volcano in Philippines

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Blast send thick column of ash 500 meters -LRB- 1,600 feet -RRB- into the air

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Mount Mayon is the most volatile of more than 50 volcanoes in the Philippines